Fuel burning apparatus



July 21, 1936.

J. EATON ETAL FUEL BURNING APPARATUS Filed Sept. 28, 1933 4/ m s m 2 Q aQ. a. v. m 2 x .s a f 5 v 5 4 m 6 v H u a a! u u 7 E 4 w v 4. II. a I .wa a z 1, m a flwwa M H v 7 bum,

Patented July 21, 1936 1 UNITED STATES PATENT OFFICE FUEL BURNINGAPPARATUS John Eaton and Walter o. Lum, Schenectady, N. Y., assignors toGeneral Electric Company, a corporation of New York Our. inventionrelates to apparatus for buming fuel, such as oil, and particularly toan improved apparatus for more emciently delivering and regulating afuel supply and for insuring proper ignition thereof, with specialprovision for protecting the elements of the apparatus against theexcessive heat encountered in operation.

More particularly our invention relates to an improved construction of aburner head wherein a fuel nozzle with its associated fuel valveoperating mechanism is mounted in a supporting frame together 'withignition electrodes and a flame responsive control switch with theelements in properly spaced relation to form a workable unit which maybe set bodily into and in sealing relation to an opening in a furnace orsimilar structure where it is desired to produce combustion. Means arealso provided in our improved burner head unit for mounting an ignitiontransformer so that its electrical contacts will directly engageconnection studs on the ignition electrodes for making electricalconnections therebetween without the use of high tension electricalleads.

One of the chief objects attained by our improved mode of correlatingthe various elements as above outlined is a compact and eflicientlyworkable burner head unit which may be initially put together by themanufacturer with the elements in their proper cooperative relation toeach other, and thereafter may be transported as a unit and installed inany desired location by unskilled labor without danger of error inassembly and adjustment.

In such a compact construction the problem of shielding the elements ofthe burner head unit from the heat of combustion and of positivelycooling various ones of the elements, is very important. Hence an objectof our invention has been the provision of effective shielding means andcooling fluid conduits which form an integral part of the unit. Inattaining this object multiwalled air insulated shielding casings havebeen mounted around the nozzle body and fuel valve operating mechanismand provision has been made for passing combustion air through thesecasings, previous to its discharge into the fuel spray, for positivelycooling the shielded elements.

An important feature of our invention is the formation of the previouslymentioned supporting frame so that it will serve as one of the shieldingcasings for a portion of the elements of the burner head.

A more detailed understanding of the manner in which the above outlinedobjects are attained may be had from the following description taken inconjunction with the accompanying drawing in which:

Fig. 1 is a sectional elevation. of a preferred embodiment of ourimproved burner head unit, taken along the line l--l of Fig. 2, showingthe details of construction thereof and the manner of mounting the unitin a vertical well in a boiler furnace structure:

Fig. 2 is a top plan view of the unit; and

Fig. 3 is an elevation of a boiler furnace partially cut away to showthe burner head unit and control apparatus mounted therein.

We have seen lit to describe and illustrate a preferred embodiment ofour improved burner head unit as utilized in conjunction with a boilerfurnace structure of the type disclosed in the copending applications ofAldo Macchi, Serial No. 676,106 flied June 16, 1933, and H. S.Woodruil', Serial No. 676,651, filed June 20, 1933, wherein our improvedburner head unit may be set in a vertical tubular well passing throughthe boiler structure in communication with the combustion chamber, andas embodying an oil nozzle of the type disclosed in the copendingapplication of Aldo Macchi, Serial No. 679,885, filed July 11, 1933, 20

all of which above referred to applications are assigned to the assigneeof the present invention. However, it is to be understood that ourinven-- tion may be applied with equal advantages to apparatus burningfuel other than 011 and in any situation where it is desired to producecombustion by means of a burner apparatus which incorporates in aunitary structure all the elements essential for most eiiicient burningof a fuel supply. Hence directional terms hereinafter used are to betaken'only as relative and are to be given their broadestinterpretation.

Referring particularly to 'Fig. 1 of the drawing, Ill represents theburner head housing or main supporting frame which is in the form of abowl for reasons to be hereinafter pointed out. This bowl is constructedwith an outwardly projecting flange II on its open end and a flangedopening I! centrally located in its closed end. Securely mounted in theopening I! and in sealing relation to the rim of the opening is atubular casing II having an inwardly tapered portion ll at the end whichprotrudes from the bowl. Nested within the bowl ll and mounted upon theend of thetubular casing ll opposite the tapered end portion thereofis.a second bowl I! having a cylindrical dished portion I the outer wall ofwhich is adapted to iit into and tightly engage the end of the tubularcasing 13. A cover I! is placed over the open end of the'bowl I! to sealthe interior thereof from atmosphere, this cover being held in place bymeans of nuts II which engage bolts 2| secured in the bowl Ii. Restingon the upper side of-the cover I! is an oblong plate 22 of electricalinsulating material, such as balrelite, having an upturned rim 23, anddepending from the lower side of the cover l1 into the interior of thebowl II is a nozzle connection head 24 which may be of magneticmaterial, the plate and the connection head being secured to the coverby means of clamping screws and an outwardly threaded bushing 25.

Mounted in inverted position on top of the plate 22 is an oblongcup-shaped cover 21 provided with a groove which fits over the upturnedrim 23 of the plate 22. This cover 21 is secured in place by means ofscrews 3| which engage holes in .the cover l1. A gasket 32 is placed inthe groove 30 to form a sealed junction between the plate 22 and thecover 21. The plate 22 and the cupshaped cover 21 therefore cooperate toform a sealed oil pressure chamber 33. A connection bushing 34 isscrewed into a passage drilled in the top of the cover 21 incommunication'with the interior of the chamber 33, and to this may beattached the high pressure oil supply pipe 35.

Depending from the nozzle connection head 24 is the nozzle body whichconsists of concentric tubes 35 and 31 which are mounted in thefollowing manner: The inner or oil tube 35 extends through and fitstightly into the nozzle connection head and is attached to the bushing25 so that it communicates with the interior'of the oil chamber 33. Thebushing 25 also forms a seal around the'tube where it passes through theplate 22, thus preventing escape of oil from the chamber 33 exceptthrough the tube. The outer or atomizing air tube 31 has a flared headwhich is mounted in a chamber 4i drilled into the lower face of thenozzle connection head 24 arid is held in place by means of externallyscrew-threaded bushing 42. A soft metal gasket 43 disposed between theflared head of the tube 31 and the end of the bushing 42 seals the airpressure chamber 4! to prevent the escape of air therefrom. a This airpressure chamber 4| is in communication, through a passage 44 drilled inthe nozzle connection head 24, with a connection bushing 45 to which maybe attached a high pressure atomizing air supply pipe 45.-

The inner nozzle tube 35 is adapted to receive oil under pressure fromthe supply pipe 35 and the oil pressure chamber 33 through the screwthreaded bushing 25 and then to discharge the oil through an orifice atits lower end. A detailed description of the operation of the nozzleincluding the manner in which the oil is atomized may be found in theaforementioned copending application of Aldo Macehi, Serial No. 679,885.

The discharge of oil from the nozzle is controlled by a plunger typevalve 41, having a valve stem which extends up through the inner nozzletube to terminate in an enlarged head 5| located in the oil pressurechamber 33. Electromagnetic means are provided for operating the valve41. In the chamber 33 is a movable magnetic armature 52 pivotallymounted on projections53 on the ends of the clamping screws 25.

One end of the armature engages the enlarged head 5| of the valve stemand the other end extends into operative relation with a magnet coil 55,which, however, is located outside of the chamber 33. This coil 55 iswound around the magnetic core 51 and is mounted in the sealed.

interior of the bowl l5, the core being supported on the lower side ofthe cover l1 by means of the screw 60, the head SI of which is providedwith a v shading coil 5|" and protrudes into the chamber 33 to serve asa. pole piece for the 'magnet.

tionhead 24 and the core 51 and is spaced therefrom by means ofnon-magnetic washers 59.

This strip completes a magnetic path between the magnet core and theconnection head with small nozzle.

gaps inserted therein by-means of the washers 55. It will be seen,therefore,-that we have in our preferred embodiment included the nozzleconnection head 24, of magnetic material, in the flux circuit of theelectromagnet thus enabling us to secure added compactness andefllciency of design while maintaining the coil 55 entirely out ofcontact with the fuel. In addition we have found that our improved typeof electromagnetic valve operating mechanism as herein described hasgreat nism, and we have found that our pivoted type of armature requiresmuch less energy for operation than the solenoid type of armature.

Energization of the electromagnet 55 will cause attraction of theassociated end of the armature 52 which causes the armature to pivot"about its fulcrum 53 to raise the valve stem 50 and'valve- 41 againstthe action of a spring 54 which is seated in a depression 55 in thecover 21 and this will permit fuel to flow from the oil pressure chamber33 through the inner nozzle tube 35 be discharged from the end thereof.

An opening 53 is provided in the cover l1, the outer edge of the openingbeing constructed in the form of a flange 53' for the connection of aconduit for the supply of low pressure combustion air (primary air) tothe interior of the bowl l5.

,A plurality 'of holes 54 are punched in thedished portion l5 of thebowl l5 to permit the passage of the primary air from the interior ofthe bowl l5 into the interior of thetubular casing i3 from which aportion of the air is discharged through the inwardly deflecting end Mof the casing in an annular sheet around and into the fuel dischargedfrom the nozzle. Between the nozzle body and the tubular casing I 3andconcentric therewith is placed an intermediate tubularcasing 55 whichis mounted on the lower reduced end portion of the bushing 42 by meansof screws 55 and which is provided with a plurality; of holes 10adjacent the upper end thereof. Adjacent the lower end i of the casing55 are internally proiectingflns 1| which serve to hold the casing inspaced relation with the nozzle body, and the discharge end of thecasing is tapered inwardly as shown at 12 to direct a flow of air fromthe casing in an annular sheet around and into the fuel discharged fromthe A disk 51, secured between the casings 55 and I3 ata pointbelow-theholes 10. in the casing 55 and-approximately opposite the lune- Q tionbetween the casing i3 andthe bowl I! to holdthe casings rigidly inposition with relation to each other, is provided with punched-out holes13 of such number andarea that the summasummation of the areas of theholes54, thus restricting the flow of air between the casings l3 s and55 and causing a flow of a portion of the air tion of the areas ofthese'holes is less than the through holes 10 into the interior ofthecasing 55 around the nozzle body.

Two ignition electrodes 14 are securely mounted in openings in theclosed end of the bowl II and are sealed in place by means of clampingnuts 15. The upper or body portions of these electrodes extend up intothe inside of the bowl while the lower ends of the ignition electrodesextend externally of the bowl and are provided with spark points 'IIprojecting into operative relation with the discharge end of the nozzleto ignite the fuel discharged therefrom. A tubular shield 18 of heatresisting material is provided to shield the lower portions of theignition electrodes from the heat of combustion. Thus the electrodes areso mounted that their body portions are out of the path of the fuel andprotected from heat and that their spark points are also flxed out ofthe path of the fuel, the natural action of the nozzle discharge beingdepended upon in a well known manner to draw the are between theelectrodes into the fuel spray.

Also mounted within the interior of the bowl I ii and shielded from theheat of combustion is a control switch mechanism 86 held in place by theclamping plate 8| mounted on the upper surface of the cover 21 by meansof the screw stud l2.

Clamping plate 8| is braced in position by means of a supporting member63. Associated with this control switch mechanism is a flame responsivedevice which extends through an opening in the closed end of the bowl I0 into such proximity with the discharge end of the nozzle that it doesnot come in contact with the fuel but will be quickly responsive to thepresence or absence of a flame at the nozzle tip.

The flame responsive device consists of a low expansion rod 84 enclosedin a corrosion resisting metal tube 85 which is mounted in an opening inthe closed end of the bowl I0 and held in place by nut 86 which sealsthe opening; The metal tube responds to temperature changes'to a muchgreater extent than does the rod. the resulting relative motion betweenthe two being used to actuate a contact arm 31 of the control switchmechanism when the tube is subjected to heat from the flame resultingfrom combustion of :the mixture discharged from the nozzle. Move- 'mentof the arm 81' causes it to engage either contact 90 or contact 9ieither one of which contacts may be designated the cold contact and theother the hot contact in a burner control circuit of the type disclosedin the copending application of Chester I. Hall, Serial No. 439,497,filed February 20, 1930, which is assigned to the assignee of thepresent invention. The contacts 61, 90 and 9| are connected by means oflead wires 81', 90' and ill'respectively through cable 62 to a mastercontrol unit hereinafter referred to.

Electrical energy is supplied from the master control unit to theelectromagnetic valve operating means 56 by means of cable 33 whichpasses through an opening in the cover I! sealed by means of the packingplate 64 which is secured in place on the cover by screws 65.

Two angle-shaped supporting arms 96. are mounted on the rim II of thebowl I 0 and serve to support an ignition transformer in proximity tothe connection studs on the ignition electrodes.

The following constitutes a description of the manner in which ourimproved burner head unit may be incorporated in a boiler'furnace of thetype described in the previously referred to copending applications ofAldo Macchi and H. S. Woodruif. Referring particularly to Fig. 3 of theaccompanying drawing, I00 represents a boiler furnace unit having acombustion chamber IIII and a boiler chamber I02. Above the furnaceproper is a control chamber I03 formed by the dome I04. The boilerfurnace proper is made up of an inner boiler shell I65 having anaperture I66 in the top thereof and an outer boiler shell I01 having anaperture therein in alignment with the aperture I06. Securely mounted inthe aperture in the shell I 01 and resting on the rim of the opening I06in the shell I66 is a tubular well III! which communicates with thecombustion chamber and which provides a seat for the burner head unit.The space between the inner shell I05 and the outer shell I0! ispartially or wholy fllled with water which thereby forms a partial orcomplete water backing for the tubular well IIII resulting in highefllciency of heat transfer from the combustion chamber to the boilerchamber.

Over the top of the boiler furnace proper and resting upon the shell I0!is placed a layer of insulation material III and a sheet metal drainplate II2. Internally of the dome and mounted of the burner head housingIll resting upon the rim of the tubular well III! to seal the openinginto the furnace. Clamping bars I I5 are provided on the outer surfaceof the outer shell I01 to engage cut-out portions H6 in the rim of thebowl I6 and the burner head unit is securedjn place by means of clampingwashers I 20 and bolts I2I with sleeves I22 disposed between the headsof the bolts and the washers.

Detachably mounted on the supporting arms 96 on the rim of the bowl I6is an ignition transformer I23 having on the bottom side thereof springcontacts I24 which are adapted to directly engage the studs 16 on theupper ends of the ignition electrodes 14 when the ignition transformeris mounted in place. This provides a short and convenient connectionbetween the ignition transformer and the ignition electrodes and makesit possible to dispense with dangerous high when the burner head unit isin place in the well III) simple connections may be made thereto to putthe burner in operative condition. A flexible metal conduit I25 isprovided to conduct low pressure or primary air from the blower to theinterior of the bowl IS, the flexible conduit being secured at its lowerend to the flanged rim 63' of the opening 63 in the cover I'l. I26represents a flexible copper tube for supplying fuel from a reservoirnot shown to the combined fuel and air pump I I3, and 35 and 46represent similar copper tubes for respectively conveying fuel andatomizing air under pressure from the pump to the burner head. I26represents a lead for conveying electrical energy from any suitablesource not shown to the master controller unit; and 32, I21 and I23represent leads for conveying electrical energy from the master controlunit to the flame responsive control switch, ignition transformer andblower motor respectively. As has previously been pointed out provisionis made for quickly and easily attaching the various electrical leadsand air and oil supply tubes to the burner head when the latter is inposition in the boiler furnace structure. The dome I04 may be secured inplace over the control apparatus on top of the furnace by means of thewing nut I36 which engages the stud 82 previously mentioned as beingmounted upon the cover 21. i

From the foregoing description it will be seen that we derive pronouncedadvantages from our 'passage of the primary air through these casingswill carry the heat away from the nozzle and the casings and prevent toa large extent the transfer of heat from the outer casing to the innercasing and from the inner casing to the nozzle. Due to the coolingeffect of the primary air and shielding of the nozzle, the nozzle ismaintained at a temperature well below the carbonizing point of the oil.a

Bowls l0 and I5 also provide a double walled shield for theelectromagnetic valve operating mechanism. Since the bowls are spacedapart and the outer bowl I0 is open to atmosphere, an insulating body ofair is provided between the bowls which will largely prevent thetransfer of heat from the outer bowl to the inner. bowl. In addition theouter bowl is in contact with the rim of the well H0 so that heat willbe conducted from the bowl to the wall of. the well and thence to theliquid within the boiler chamber. Furthercooling of the magnet coil andupper nozzle structure is secured by the passing of the primary airthrough the inner bowl over the coil and nozzle connection head wherebyheat is conducted away from these elements and transfer of heat to themfrom the inner bowl is also pre-:

vented. In passing through the bowl and the tubular casings the primaryair becomes preheated from the heat given off by the various elementsand the discharge of such preheated air into the fuel spray deliveredfrom the nozzle further adds to the efflclency of the operation of maybe made in the preferred form of our im- Y proved burner head unitherein described without departing from our invention andit is intendedthat theseshall be included within the scope of the following claims inwhich we set forth those features which we believe to be new in the art.a

What we claim'as new and desire to secure by Letters Patent of theUnited States, is:.

1. A fluid fuel burner head unit for a furnace including in combinationa bowl-adapted to close an opening in the furnace, a fuel deliverynozzle mounted in the bowl and extending through the fuel ignitingmeans.

2. A fluid fuel burner head unit for a furnace including in combinationan enclosing bowl having a flanged rim for mounting the bowl to seal anopening into the furnace, a fuel delivery nozzle mounted in the bowl andextending through the end wall thereof for delivering fuel to thefurnace, electrically operated means operatively associated with thenozzle inside the bowl for controlling the delivery of the fuel,electrical ignition means mounted in the bowl and including electrodesextending through the end wall thereof into spaced operative relationwith the delivery end of the nozzle for igniting the fuel, and meansmounted inside the bowl including a flame responsive element extendingthrough the end wall of the bowl to be responsive to flame at thedelivery end of the nozzle for controlling said fuel deliverycontrolling and ignition means.

3. A fluid fuel burner head unit including in combination, a fueldelivery nozzle, a bowl adapted to close an opening in a furnace andhaving means for supporting the nozzle inside the bowl with thedischarge end of the nozzle protruding through an opening in the endwall of the bowl, ignition electrodes mounted in the bowl with one endof each thereof extending through the end wall of the bowl into spacedoperative relation with the discharge end ofthe nozzle, connection studson the other ends of the electrodes,

an ignition transformer provided with electrical contacts, andsupporting means on the rim of the bowl for detachably mounting thetransformer with its said electrical contacts directly engaging theconnection studs of the ignition electrodes.

4. A fluid fuel burner head unit forv a furnace having an opening in thewall thereof, including in combination, a bowl having a flanged rim formounting the bowl to seal said furnace opening, a fuel delivery nozzlemounted in the bowl and extending through the end wall thereof fordischarging fuel into the furnace, electrically operated valve meansmounted inside the bowl and operatively associated with the nozzle forcontrolling the discharge of fuel therefrom, electric ignitionelectrodes supported by the bowl and extending into spaced operativerelation with the discharge end of the nozzle for igniting the fuel, andmeans mounted in the bowl including a flame responsive element extendingthrough the end wall of the bowl to be responsive to flame at thedischarge end of the nozzle for controlling said fuel dischargecontrolling and ignitin means.

5. A fluid fuel burner-head unit including in combination, a fueldelivery nozzle having a valve for.control1ing thedischarge of fueltherefrom,

electromagnetic means mounted in proximity to the supply end of thenozzle and connected to operate the valve, and a plurality of bowlsnested around the supply end of the nozzle and said means to form amulti-walled heat shield therefor with air spaces between the bowls,said bowls having apertures in the end walls thereof through whichextends the discharge end of the nozzle.

6. A fluid fuel burner head unit including in combination, a fueldelivery nozzle, a bowl surrounding the inlet end of the nozzle andhaving an aperture in the end wall thereof through which extends the ciischarge,end of the nozzle in spaced relation to the rim of theaperture, a cover for sealing the open end of the bowl and means foradmitting air into the interior thereof, a hollow tubular casing mountedin registry with the aperture in the end wall of the bowl and'extendingoutwardly therefrom in surrounding spaced relation to the discharge endof the nozzle to provide an air passage around e 2,048,495 the nozzle incommunication with the interior of the bowl, a second hollow tubularcasing disposed between the nozzle and the first tubular casing andextending in concentric spaced relation thereto for dividing the flow ofair through said air passage around the nozzle, and means at the outerends of said tubular casings for di-,

recting the .flow of air in an annular sheet around and into the fueldelivered from the discharge end of the nozzle.

7. A fluid fuel burner head unit including in combination, a fueldelivery nozzle having a valve for controlling the discharge of fueltherefrom, a connection head provided with means for supporting theinlet .end of the nozzle and for conveying a supply of fuel thereto,electromagnetic outer one of the bowls in surrounding spaced relation tothe nozzle and in communication with the interior of the inner one ofthe bowls to provide a double walled air insulated shield for thenozzle.

8. A fluid fuel burner head unit including in combination, a fueldelivery nozzle having valve means for controlling the discharge of fuelthere from, electro-magnetic means for operating the valve means andincluding a magnet coil mounted on the supply end of the nozzle, and anair conduit surrounding the magnet coil and the nozzle for directing aflow of cooling air over the magnet coil and around the fuel dischargedfrom the ported adjacent the nozzle, a conduit surrounding the nozzlefor conducting combustion air into intimate contact with the fueldischarged from said nozzle, and means for cooling said coil including acasing surrounding the magnet coil' for directing a flow of airthereover and connected to supply air to said combustion air conduit.

10. A fluid fuel burner headunit including in combination, a fueldelivery nozzle having a valve for controlling the discharge of fueltherefrom,

electro-magnetic means for actuating the valve including an operatingmechanism supported adjacent the inlet end of the nozzle, a pair ofbowls in surrounding relation to said mechanism and said inlet end ofthe nozzle with an air space between the end walls 'of the bowls to forma double walled heat shield for said mechanism,

said bowls having apertures in the end walls thereof through whichextends the discharge end of the nozzle, and ignition electrodes mountedin the outer of the bowls and extending outwardly through the end wallthereof into spaced operative relation with the discharge end of thenozzle. 11.: A fluid fuel burner head unit including in combination, afuel delivery nozzle, a connection head of magnetic material surroundingthe supply end of the nozzle and secured thereto, means pro= viding afluid-tight fuel storage chamber mounted on said connection head incommunication with the nozzle, a valve for controlling the discharge offuel from the nozzle, means for actuating said valve including amagnetic member operatively connected thereto and movably mounted withinsaid chamber, means for actuating said magnetic member including amagnet coil disposed ad- -jacent said connection head externally of saidchamber and in operative elation to said magnetic member, and'meansincluding said connection head for completing the magnetic circuit forthe flux produced by said magnet coil.

12. A fluid fuel-burner head unit including in" 1 combination, a fueldelivery nozzle, a connection head of magnetic material surrounding thesupply end of the nozzle and secured thereto, means providing afluid-tight fuel storage chamber mounted on said connection head incommunication with the nozzle, a valve for controlling the discharge offuel from the nozzle, means for actuating said valve including amagnetic member operatively connected thereto and movably mounted withinsaid chamber, means for actuating said magnetic member including amagnet coil disposed adjacent said connection head ex- I ternally ofsaid chamber and in operative relation to said magnetic member, meansincluding said connection head for completing the magnetic circuit forthe flux produced by saidmagnet coil, and heat protective means for saidconnection head and said magnet coil including a combustion air supplycasing disposed thereardund and provided with means for directing astream of combustion air adjacent the discharge end of the nozzle. f 1

13. A fluid fuel burner head unit including in combination, a fueldelivery nozzle having'a fluid conducting passage and a valveoperatively asso' ciated therewith for controlling the discharge of fueltherefrom, means providing a fluid-tight chamber adjacent the supplyendof he nozzle and communicating with said passage, and electromagneticmeans for operating said valveincluding a magnetic member pivotally.mounted in said chamber with one end operatively connected to saidvalve and a cooperating magnetic structure having one portion thereofextending into said chamber adjacent, the pivotal mounting of, saidmagnetic member and haviiig another portion with an energizing windingthereon mounted externally of said chambefin operative relation to theother end of said magnetic member.

14. A fluid fuel burner head unit including in combination, a fueldelivery nozzle and a valve' operatively associated therewith forcontrolling the discharge of fuel therefrom, a connection head ofmagnetic material mounted in surrounding relation to the supply end ofthe nozzle, means providing a fluid-tight fuel storage chamber mountedon said connection head in communication with the nozzle, and means foroperating said valve including an electromagnetic armature pivotallymounted within said chamber with one end connected to said valve and amagnetic energizing coil disposed outside of saidchamber in operativerelation to the free end of said armature, said connection headbeingarranged to

